Super single tires, which are wide base low aspect ratio truck tires replacing two small base tires, so-called dual mounted tires, have been used for years on trailers. Such tires are usually of size 385/65R22.5 or 385/55R22.5 and have a maximum load-carrying capacity of 4.5 metric tons.
Over the years these wide base tires appeared more and more on trucks in the steering position because they had an expected higher mileage.
Recently it became of interest to use also super single tires in the drive positions.
Tires in the drive position have to bear part of the trailer load and must have an increased load capacity. Tire standards define a load capacity of 5.8 metric tons and a maximum speed of 110 km/h. These tires have very low aspect ratios and are usually of size 495/45R22.5. Drive tires are exposed to harsh service conditions and conventional constructions show crown area durability problems. Furthermore, the pressure distribution through the elastomeric blocks in the footprint lacks the required uniformity.
US 2005/0126674 A1 discloses a pneumatic truck tire, in particular a super single radial truck tire. The tire comprises a crown reinforcing structure including a single helically wound belt ply reinforced with high elongation steel cords. In one embodiment of this publication, the tire comprises four belts on top of two steel strips. The strips are located between the carcass ply and the radially inner helically wound ply. Although the tire disclosed in this publication might constitute an improvement with regard to earlier prior art, room for further improvements remains. In practice, respective tires may show groove cracking at the intermediate shoulder groove and/or might exhibit breaker edge separation between the two outer breakers. Furthermore, an increased wear of the shoulders may be observed.
U.S. Pat. No. 6,401,778 B1 discloses another pneumatic truck tire having a radial carcass reinforcement and two working crown plies of inextensible reinforcing elements. An additional ply essentially parallel to the circumferential direction of the tire is positioned between the two working plies. Both working plies extend axially beyond the axial width of the additional ply and are coupled with each other over an axial length of at least 16% of the maximum axial with of the carcass reinforcement. This tire design may also provide an improvement with regard to earlier truck tires. However, durability could still be improved.